Neuroanatomy 3 Flashcards
Spinal Cord: Structure
Describe the shape and organization of the spinal cord.
It is a cylindrical structure characterized by a central H shaped region of gray matter and a peripheral region of white matter. This gray matter/white matter arrangement is opposite the arrangement in the brain.
Spinal Cord: Structure
Where is it and what is it continuous with?
The spinal cord is continuous rostrally with the brainstem. It extends from the foramen magnum of the occipital bone to LV2 level. It lies in the vertebral cnal created by successive vertebral foramen.
Spinal Cord: Structure
Describe the organization of the spinal cord levels
It is divided into 31 spinal cord levels or segments: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal. The level is specified by the intervertebral foramina through which the dorsal and ventral roots attached to that segment enter the vertebral canal.
Spinal Cord: External Anatomy
Regions - Cervical Enlargement
Extends from the C4 segment to the T1 segment.
Gives rise to nerves that innervate the UE
Spinal Cord: External Anatomy
Regions - Lumbosacral Enlargement
Extends from the L1 to S2 segments.
Gives rise to nerves that innervate the LE
Spinal Cord: External Anatomy
Regions - Medullary Cone
Tapering inferior end of the spinal cord at about the level of LV2
Spinal Cord: External Anatomy
Regions - Cauda Equina
aka Rootlets
It is composed of the dorsal and ventral roots arising from the lumbosacral enlargement and the medullary cone.
Spinal Cord: External Anatomy
What fissures/sulci are on the ventral surface?
Anterior median fissure - continuous with the anterior median fissure of the medulla
Anterolateral sulcus - this is where the ventral roots emerge
Spinal Cord: External Anatomy
What fissures/sulci are on the dorsal surface?
Posterior median sulcus - continuou with the posterior median sulcus of the medulla
Posterolateral sulcus - this is where the dorsal roots emerge.
Spinal Cord: External Anatomy
Spinal Nerves - How many are there? Where are they found?
There are 31 pairs of spinal nerves
They occupy the space within the intervertebral foramen created by the vertebral notches of successive vertebrae.
C1 - C7 are located ABOVE the vertebrae of the same number, C8 is below CV7, and T1 - L5 are located BELOW the same numbered vertebrae
There is only about 1 com of that we call the “spinal nerve” where the dorsal and ventral roots come together before they split into the dorsal and ventral rami. This area is MIXED (carries both sensory and motor fibers.
Spinal Cord: External Anatomy
Dorsal Roots
Carry afferent fibers from the periphery.
Cell bodies of these axons are in the dorsal root ganglia
Spinal Cord: External Anatomy
Ventral Roots
Carry efferent fibers to the periphery.
Cell bodies of these axons are in the ventral horn of the spinal cord
Spinal Cord: External Anatomy
Dorsal Primary Rami
Supply the vertebral column joints, deep back muscles, and overlying skin.
They are smaller because they innervate less.
Spinal Cord: External Anatomy
Ventral Primary Rami
Supply anterior and lateral trunk, upper limbs, and lower limbs.
Certain rami form plexes
Spinal Cord: Internal Anatomy
Gray matter - structural characteristics
Central H shaped region
Contains neuronal cell bodies, dendrites, unmyelinated axons, and glial cells
Spinal Cord: Internal Anatomy
Gray matter - where is it most predominant and why?
Greater in the cervical and lumbosacral regions due to the innervations of the UE and LE respectively.
Spinal Cord: Internal Anatomy
Gray matter - Dorsal Horn
Sensory
Neurons in the dorsal horn receive the central processes of the neuron cell bodies in the dorsal root ganglia through the dorsal roots
Spinal Cord: Internal Anatomy
Gray matter - Ventral Horn
Motor neurons send their axons from the ventral horn towards the periphery via the ventral roots
Spinal Cord: Internal Anatomy
Gray matter - Lateral Horn
The lateral horn is present ONLY in the thoracic region from T1 to L2.
The motor neurons here send their axons to autonomic ganglia through the ventral roots.
Spinal Cord: Internal Anatomy
White Matter - Structure, contents
It is the peripheral region of the spinal cord (including the anterior white commisure)
It contains myelinated axons and oligodendrocytes
Spinal Cord: Internal Anatomy
White matter - in which direction does the white matter increase and why?
Increases from sacral to cervical regions as the volume of sensory fibers increases at each ascending level and motor fibers decrease at each descending level.
Spinal Cord: Internal Anatomy
White matter - How is white matter subdivided?
Subdivided into funiculi, fasciculi, and tracts
Spinal Cord: Internal Anatomy
White matter - Dorsal Funiculus
Carries ascending sensory information
Spinal Cord: Internal Anatomy
White matter - Lateral Funiculus
Carries ascending sensory information and descending motor information
Spinal Cord: Internal Anatomy
White matter - Ventral Funiculus
Carries ascending sensory information and descending motor information
Spinal Cord: Functions
1) Carries sensory information from the extremities, trunk, and viscera to the brain
2) Conveys motor information to the extremities, trunk, and viscera
3) Site of spinal reflexes which are essential to normal function
4) Conveys modulatory information from the brain - the brain controls what is going on in the spinal cord
Ventricular System: definition
Continuous fluid filled system in the CNS lined with ependymal cells.
Ventricular System: Structures
Lateral Ventricles (2)
Associated with the telencephalon
C-shaped structures separated by the septum pellucidum
Ventricular System: Structures
Interventricular foramina (2)
Aka foramina of Munro
Connect the lateral ventricles to the third ventricle
Ventricular System: Structures
Third Ventricle
Associated with the thalamus and hypothalamus
It is a thin, midline structure
it is interrupted with the interthalamic adhesion adhesion that connects the 2 thalmi
Ventricular System: Structures
Cerebral Aqueduct
aka aqueduct of Sylvius
Connects the 3rf ventricle to the 4th ventricle
Associated with the midbrain
Ventricular System: Structures
4th Ventricle
Associated with the pons and medulla
Pyramid shaped space covered on its dorsal aspect by the cerebellum
Continues into the central canal of the spinal cord, which does not remain fully patent beyond the early postnatal period
Opens into the subarachnoid space through laterally placed foramina of Luschka and the medial foramen of Magendie
CSF - Where is it formed?
CSF is formed in the Choroid plexes, which are located in the ventricles.
Choroid plexes are composed of the endothelial walls of capillaries, pia mater, and choroid epithelial (specialized ependymal) cells
CSF - What is the composition of CSF?
It is a clear, colorless liquid.
Low in cells and protein.
Similar to plasma in ion concentration.
CSF - How does CSF circulate? Describe the sequence.
Flows freely from the ventricular system into the subarachnoid space where it is taken up into the venous system by arachnoid villi.
Flow:
1) Lateral Ventricles
2) Interventricular foramina
3) Third Ventricle
4) Cerebral Aqueduct
5) Fourth Ventricle
6) Foramen of Magendie and Foramina of Lushcka
7) Subarachnoid space
8) Venous system
CSF - How is it absorbed?
It is absorbed into the venous system at the superior sagittal sinus through arachnoid granulations, which consist of collections of arachnoid villi that protrude through the dura mater into the sinuses
CSF - Function
1) Mechanically supportive of the brain due to its buoyant effect
2) Maintenance of the extracellular environment
3) Route for the spread of neuroactive hormones through the CNS
Meninges: What are the three meningeal layers?
Dura mater, Arachnoid Mater, Pia Mater
Meninges: Dura mater
Structural specializations - What are Dural Infoldings?
These exist in the BRIAIN ONLY
The inner portions of the dura mater give rise to septa that separate brain regions from each other and contain venous sinuses.
Meninges: Dura mater
Structural specializations - Dural infoldings –> Falx cerebri
Located between cerebral hemispheres
Meninges: Dura mater
Structural specializations - Dural infoldings –> Tentorium Cerebelli
Located between the cerebral hemispheres and the cerebellum
Meninges: Dura mater
Structural specializations - Dural infoldings –> Falx cerebelli
between the cerebellar hemispheres
Meninges: Dura mater
Structural specializations - Dural Sac
This is in the SPINAL CORD ONLY
It is a tubular sheath surrounding the spinal cord in the vertebral canal.
It is anchored rostrally to the foramen magnum, and cadally to the coccyx via the filum terminal externum which is composed of dura mater as well
Meninges: Dura mater
Spaces - Subdural
Potential space between the dura mater and the arachnoid mater
Meninges: Dura mater
Spaces - Epidural Space
This exists in the SPINAL CORD ONLY
It is the space between the dura mater and the vertebral canal
Meninges: Arachnoid mater
Arachnoid Trabeculae - definition
CT strands that connect the arachnoid mater to the pia mater
Meninges: Arachnoid mater
Arachnoid Villi - definition
These are in the BRAIN ONLY
The are specializations of the arachnoid that are structurally adapted for transporting CSF from the subarachnoid space into venous circulation.
Meninges: Arachnoid mater
Subarachnoid Space
Space between the arachnoid mater and the pia mater.
Contains CSF
Meninges: Arachnoid mater
Cisterns - Definition; names and locations of 2 cisterns
Dilations within the subarachnoid space
Cisterna Magna - Dorsal to the medulla
Lumbar - Caudal to the Medullary Cone
Meninges: Pia mater
Specializations - denticulate ligaments
These are in the SPINAL CORD ONLY
They are extensions from the lateral surfaces of the pia mater to the dural sac
Meninges: Pia mater
Specializations - filum terminal internum
This is in the SPINAL CORD ONLY
A tough strand of the pia mater that anchors the medullary cone to the caudal end of the dural sac
Located in the cauda equina
Meninges: Function
Stabilize the shape and position oft he CNS during head and body movements.
Vasculature of the Brain
How much of the body weight is the brain? How much blood does it receive? How much oxygen does it use? What does this reflect?
The brain is only 2% of the total body weight but it receives about 15% of the total CO and consumes about 20% of the oxygen used by the entire body.
this reflects the high metabolic rate and therefore oxygen requirements of the brain
Vasculature of the Brain
What happens when the Brian is deprived of blood for certain amounts of time?
10 seconds - loss of consciousness
3-5 min - irreparable brain damage or death may result
Vasculature of the Brain
Arteries: Internal Carotid
Origin
Course
Branches
Constitutes the anterior circulation of the brain
Origin:
Right - Brachiocephalic trunk
Left: Arch of the aorta
Course: Ascends through the anterior triangle of the neck, enters the carotid canal of the temporal bone, traverses the cavernous sinus, the pierces the dura mater
Branches: Ophthalmic Posterior Communicating Middle Cerebral Anterior Cerebral
Vasculature of the Brain
Arteries: Internal Carotid - Ophtalmic branch
Course
Distribution
Course: Branches from the internal carotid rostrally and travels with CNII through the optic canal into the orbit; anastomoses with the facial artery (communication between internal and external carotid arteries.
Distribution: Orbit (only artery that is not a branch of the facial nerve that has any distribution in the face)
Vasculature of the Brain
Arteries: Internal Carotid - Posterior communicating branch
Course
Distribution
Course: Connects the internal carotid artery to the posterior cerebral artery
Distribution: n/a
Vasculature of the Brain
Arteries: Internal Carotid - Middle Cerebral branch
Course
Distribution
Course: This terminal branch comes off laterally and proceeds through the lateral sulcus extending laterally to spread out over the lateral surface of the cerebral hemisphere.
Distribution: Lateral convexity of the cerebral cortex; Internal Capsule, Basal Ganglia
Vasculature of the Brain
Arteries: Internal Carotid - Anterior Cerebral branch
Course
Distribution
Course: This terminal branch proceeds into the longitudinal fissure, loops around the medial surface of the cerebral hemisphere, and runs just superior to the corpus callosum.
Distribution: Medial frontal and parietal cerebral cortex; Internal capsule, basal ganglia, hypothalamus
Vasculature of the Brain
Arteries: Vertebral
Origin
Course
Branches
Constitutes the posterior circulation of the brain
Origin: Subclavian Artery
Course: Ascend through the transverse foramina of the cervical vertebrae and enter the cranium through the foramen magnum.
Branches: Anterior Spinal Posterior Inferior Cerebellar (PICA) Posterior Spinal Basliar Posterior Cerebral
Vasculature of the Brain
Arteries: Vertebral - Anterior Spinal branch
Course
Distribution
Course: Joints counterpart from the opposite side and runs caudally along the midline of the spinal cord
Distribution: Anterior 2/3 of the spinal cord
Vasculature of the Brain
Arteries: Internal Carotid - Posterior Inferior Cerebellar (PICA) branch
Course
Branch
Distribution
Course: arches around the dorsolateral medulla
Branch: Gives off the POSTERIOR SPINAL branch, which runs caudally along the posterolateral aspect of the spinal cord and supplies the posterior 1/3 of the spine
Distribution: Dorsolateral medulla; cerebellum
Vasculature of the Brain
Arteries: Vertebral - Basilar branch
Course
Distribution
Course: Formed from the fusion of the vertebral arteries at the junction of the medulla and the pons. Runs in the ventral midline of the pons.
Distribution: n/a
Vasculature of the Brain
Arteries: Vertebral - Posterior Cerebral branch
Course
Distribution
Course: This terminal branch passes lateral just rostral to the occulomotor nerve. It connects to the posterior communication branch of the internal carotid artery, completing the circle of Willis.
Distribution: Midbrain, Thalamus, Occipital and Inferior temporal cerebral cortex
Vasculature of the Brain
Arterial anastomoses - Circle of willis
Located on the ventral surface of the brain, surrounding the optic tracts, infundibulum, and basal hypothalamus.
Vasculature of the Brain
Watershed border zones
Regions of the lateral surface of the cerebellar hemisphere where the terminal branches of the anterior, middle, and posterior cerebral arteries terminate.
Vasculature of the Brain
Veins - Where do they empty into?
Veins empty into venous sinuses
Vasculature of the Brain
Sinuses - where are they? What is their purpose?
Sinuses are located between the inner and outer layers of dura mater.
They serve as conduits to drain venous blood from the brain into the internal jugular veins
Vasculature of the Brain
Sinuses - Superior Sagittal Sinus
Location
Termination
Location: ATTACHED edge of the falx cerebri
Termination: Confluence
Vasculature of the Brain
Sinuses - Inferior Sagittal Sinus
Location
Termination
Location: Free edge of the falx cerebri
Termination: Straight Sinus
Vasculature of the Brain
Sinuses - Straight Sinus
Location
Termination
Location: where the falx cerebri attaches to the tentorium cerebelli
Termination: Confluence
Vasculature of the Brain
Sinuses - Transverse Sinus
Location
Termination
Location: Courses laterally from the confluence sinus in a shallow groove on the internal surface of the occipital bone.
Termination: Sigmoid
Vasculature of the Brain
Sinuses - Confluence Sinus
Location
Termination
Location: Junction of the superior sagittal, straight, and transverse sinuses
Termination: Transverse Sinus
Vasculature of the Brain
Sinuses - Sigmoid Sinus
Location
Termination
Location: Courses inferiorly from the transverse sinus in a shallow groove on the internal surface of the temporal bone, and traverses the jugular foramen.
Termination: Internal Jugular
Vasculature of the Brain
Sinuses - Cavernous Sinus
Location
Contents
Termination
Location: Side of the sphenoid bone.
Contains the internal carotid artery, CN3, 4, and all 3 parts of 5
Termination: Superior petrosal and inferior petrosal into the sigmoid sinus
Vasculature of the Brain
Blood Brain Barrier - structure
1) There are tight junction between the capillary endothelial cells in the brain.
2) the capillaries are lined with astrocytes, whose endfoot processes are very closely associated with the endothelial cells, creating a barrier
Vasculature of the Brain
Blood brain barrier - function
Highly selective barrier
Vasculature of the Spinal Cord
Arteries - how many longitudinal ones are there anteriorly and posteriorly? Where do they extend from/to?
There are one and anterior and 2 posterior longitudinal arteries associated with the spinal cord.
They run from the medulla to the medullary cone of the spinal cord.
Additional arteries run horizontally along the spinal nerve roots
Vasculature of the Spinal Cord
Arteries - anterior spinal
Origin
Course
Distribution
Origin: Vertebral
Course: Joins counterpart from the opposite side, runs caudally along the midline of the spinal cord
Distribution: Anterior 2/3 of the spinal cord
Vasculature of the Spinal Cord
Arteries - Posterior spinal
Origin
Course
Distribution
Origin: PICA
Course: Runs causally along the posterolateral aspect of the spinal cord
Distribution: Posterior 1/3 of the spinal cord
Vasculature of the Spinal Cord
Arteries - Segmental Medullary
Course
Distribution
Course: Run along the spinal nerve roots, segmental medullary arteries replace radicular arteries at the irregular levels at which they occur. Otherwise, radicular occur at every level.
Distribution: Anterior and posterior spinal arteries in the cervical and lumbosacral enlargements
Vasculature of the Spinal Cord
Arteries - Radicular
Course
Distribution
Course: Run along the spinal nerve roots, segmental medullary arteries replace radicular arteries at the irregular levels at which they occur. Otherwise, radicular occur at every level.
Distribution: Nerve roots
